This invention relates to apparatus for sealing the lance port in the gas collecting hood of pneumatic steel making apparatus.
In pneumatic steel converter vessels, air or oxygen is delivered to the molten metal for oxidizing silicon, phosphorous, carbon and other impurities. In one type of pneumatic steel making process, oxygen is blown at high velocity onto the surface of the metal bath in a basic lined vessel by an elongate water-cooled lance inserted through the open mouth of the vessel. In this type of apparatus, commonly called a BOF furnace, the oxygen jet striking the bath causes reactions leading to the formation of carbon monoxide which gives rise to a vigorous boiling action. In addition, iron oxide is also formed, a portion of which issues from the vessel as a brownish smoke along with the carbon monoxide and other gases. As a result, BOF furnaces are commonly provided with a gas collecting hood disposed above the open upper end of the vessel for collecting gases and particulate material discharging from the vessel. Such gas collecting hoods are connected to gas cleaning systems which remove particulates and either flare or collect combustible gases for use as fuel.
Oxygen lances commonly employed with BOF vessels generally comprise an elongate tubular water-cooled member which is inserted longitudinally through the mouth of the vessel so its discharge end is in relatively closed proximity to the molten metal during an oxygen blowing period. After the completion of the main oxygen blow, the lance is withdrawn from the furnace to permit the latter to be tilted for sampling, deslagging, pouring and thereafter the charging of scrap and hot metal for subsequent steel making cycles. Because the gas collecting hood is preferably disposed above the open upper end of the vessel during a blowing operation to effectively capture discharging gases and particulate matter, such hoods are commonly provided with a lance port to permit the lance to pass through the hood and into the vessel. Such lance ports must be substantially larger in cross-sectional area than the lance because the lance tends to thrash about and swing in reaction to the oxygen issuing from its lower end. In addition, the lance tends to become encrusted with metal and slag during the blowing operation thereby increasing the nominal outside diameter of that portion disposed within the furnace and below the lance port. For this reason, a gap normally existed between the lance and the lance port during a blowing operation which permitted some polluting gases and particulate matter to escape from the smoke hood.